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/*! \file
  \brief Functor performing conversion operations used by epilogues.
*/

#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/numeric_types.h"
#include "cutlass/array.h"
#include "cutlass/functional.h"
#include "cutlass/numeric_conversion.h"

/////////////////////////////////////////////////////////////////////////////////////////////////

namespace cutlass {
namespace epilogue {
namespace thread {

/////////////////////////////////////////////////////////////////////////////////////////////////

/// Converts the result without other operations
///
template <typename ElementOutput_,  ///< Data type used to load and store
                                    ///< tensors
          int Count,  ///< Number of elements computed per operation
          typename ElementAccumulator_ =
                  ElementOutput_,  ///< Accumulator data type
          FloatRoundStyle Round = FloatRoundStyle::round_to_nearest>
class Convert {
public:
    using ElementOutput = ElementOutput_;
    using ElementAccumulator = ElementAccumulator_;
    using ElementCompute = ElementAccumulator_;

    static int const kCount = Count;

    using FragmentOutput = Array<ElementOutput, kCount>;
    using FragmentAccumulator = Array<ElementAccumulator, kCount>;
    using ComputeFragment = FragmentAccumulator;

    static FloatRoundStyle const kRound = Round;

    /// Host-constructable parameters structure
    struct Params {
        //
        // Methods
        //

        CUTLASS_HOST_DEVICE
        Params() {}
    };

public:
    /// Constructs the function object, possibly loading from pointers in host
    /// memory
    CUTLASS_HOST_DEVICE
    Convert(Params const& params = Params()) {}

    /// Returns true if source is needed based on state of runtime arguments
    CUTLASS_HOST_DEVICE
    constexpr bool is_source_needed() const { return false; }

    /// Constexpr function to enable the compiler to optimize away the source
    /// loading if it is never needed.
    CUTLASS_HOST_DEVICE
    constexpr bool is_source_ever_needed() const { return false; }

    /// Computes linear scaling: D = alpha * accumulator + beta * source
    CUTLASS_HOST_DEVICE
    FragmentOutput operator()(
            FragmentAccumulator const& accumulator,
            FragmentOutput const& source = FragmentOutput(),
            ElementCompute uniform = ElementCompute(0)) const {
        // Convert to destination numeric type
        NumericArrayConverter<ElementOutput, ElementAccumulator, kCount, Round>
                destination_converter;

        return destination_converter(accumulator);
    }
};

/////////////////////////////////////////////////////////////////////////////////////////////////

}  // namespace thread
}  // namespace epilogue
}  // namespace cutlass
